1. Field of the Invention
This invention relates to methods and apparatus of trocar devices and more specifically, arrangements to increase the efficiency of a pneumoseal (no seal) cannula when used in conjunction with a multitude of other various different ID sized cannulae.
2. Prior Art
The primary goal of cannula seals for laparoscopic, or minimally invasive surgery is to maintain gaseous distention of the abdominal cavity adequately for an operative pneumoperitoneum. An operative pneumoperitoneum is the maintenance of adequate vision and access to anatomic structures for surgical manipulation despite the frequent exchange of instruments through those cannula seals. As described in our above identified co-pending U.S. patent applications relating to an active pneumoseal, an infused distention gas is directly borne through a trocar arrangement to create a non-mechanical seal and to maintain an operative pneumoperitoneum in a patient being operated upon. This is a viable alternative to existing seal technology. A prototype pneumoseal trocar arrangement has displayed a surprising reserve capacity in both bench and animal lab testing. Results from these tests showed that the pneumoseal (no mechanical seal) cannula was able to maintain an operative pneumoperitoneum despite a free loss of distention gas through a multitude of other medium bore (5 mm) non-sealed cannulas arranged in a test situation. In fact, three 5 mm non-sealed cannulas and a 12 mm pneumoseal were utilized while still maintaining an operative pneumoseal with the pneumoseal trocar of the present invention. (This is like operating through ordinary soda straws if used in conjunction with a pneumoseal 12 mm cannula.)
The efficiency of any cannula seal system in a normal operative environment can best be described as a function of three variables: 1) the volume of distention gas infused into the operative pneumoperitoneum; 2) the volume of gas lost from the operative pneumoperitoneum; 3) the maintenance of the operative pneumoperitoneum adequate for uninterrupted surgical tasks. The pneumoseal arrangements of the present invention utilize a high flow of distention gas in a large bore cannula to create a wall of air preferably at an angle with respect to the longitudinal axis of the cannula. In conventional mechanical seal technology, a low flow of distention gas is insufflated into the patient through a separate cannula, which gas used to maintain an operative pneumoperitoneum. Medical instruments for the operative procedure are introduced into the patient through a trocar, and each singular instrument must be passed through a valve like mechanical seal such as a duck bill valve, a slit-like valve or a flap valve, in an attempt to maintain the pneumperitoneum. Any gas lost from the operative pneumoperitoneum is therefore detrimental to the operation, and must be addressed (re-introduced) before surgery can resume. In a typical laparoscopic surgical procedure, many different cannulae are used. A partial obstruction of the outflow of distending gas from the pneumoperitoneum in one or all of the cannulae used would increase the overall efficiency of the cannula system. The pneumoseal technology of the present invention provides this partial obstruction while maintaining an adequate operative pneumoperitoneum. Such a partial obstruction typically would fail using current mechanical seal technology. In the mechanical seal technology of the prior art, any loss of distending gas completely destroys the operative pneumoperitoneum. In fact, currently available cannulas have a dual mechanical seal to maintain an operative pneumoperitoneum. The seal is so critical that a defect of 1 mm or less in any part of the system is enough to render the pneumoperitoneum inoperative.
Currently available airtight cannulae use two valves per cannula to insure the maintenance of an operative pneumoperitoneum. The proximal “universal seal” of the prior art is shown in Applied Medical Corporation patents '553 and '850, with a floating valve to completely seal around round instruments from 5 mm to 12 mm outside diameter. The introduction of an instrument through these prior art seals decreases the efficiency of the distal airtight seal, whether the seal is a “flap” valve or a “duck bill” valve. This is because each of these types of distal prior art valves do not conform to the complete outer circumference of any instrument introduced through that valve. Without an instrument in the cannula channel, the proximal valve of the prior art maintains a 4 mm opening. The operative pneumoperitoneum is maintained by the airtight flap valve or duckbill valve in the channel of the cannula. The efficiency of the seal is somewhat lost because the air input in these cannulas of the prior art is proximal to the valve. To increase gas in the distending pneumoperitoneum, the valve must be opened. If the gas input were positioned distal to the mechanical “flap” or “duck bill” valves, as accomplished by the present invention, the input gas would distend the operative pneumoperitoneum and close the mechanical valve with upward or “backward” pressure.
The efficiency of any pressurized space such as the operative pneumoperitoneum depends upon the gas input and gas loss. Current laparoscopic insufflation equipment interposes an electrically controlled modulating system between the high pressure/high flow gas input and the patient. Only one tube connects the insufflation equipment and the operative pneumoperitoneum, for this single tube both supplies insufflation gas and monitors the pressure within the pneumoperitoneum. Currently, the one tube system operates on a pulsitile node where the gas is insufflated for six seconds and paused for two seconds. The pressure node is to be able to measure the back pressure in the single tube, an indirect measurement of the pressure in the operative pneumoperitoneum. This arrangement decreases the efficiency of the pressurized space, for the inflow of gas to supply and support the pneumoperitoneum is only available 70 to 80% of the time. A more efficient system would be one aspect of the present invention wherein a two tube arrangement having one tube or cannula to supply the pneumoperitoneum is a dedicated supply line and the second tube is a dedicated pressure monitoring line. In such a two line system of the present invention, the input efficiency would rise to 100% of gas insufflation. In addition, the pressure measuring line would be constant, not intermittent, and therefore pressure measurements would occur in real time.
In a further aspect of the present invention of the two line system, an input gas supply line and an output, intra-abdominal pressure sensing line may be connected with a mechanical modulating device without having to rely upon the current electrical control of gas input of the prior art.
Also, with a two line system of the present invention, the pressure measuring line may be connected to a double lumen cannula, or alternatively, to a separate pneumoperitoneum measuring dedicated cannula, or alternatively, again for example, the pressure measuring line may be connected to a free standing trans-abdominally placed, intra-peritoneal sensor. Either of these alternative preferred embodiments will permit both continuous direct intra-abdominal pressure measurements through one line, and the continuous direct insufflation of gas to the pneumoperitoneum, to increase the gas input to 100% efficiency.